1. Field of the Invention
The invention is in the field of test devices, or respectively test adapters for testing integrated circuits (IC) such as computer chips and (micro) processors.
2. Discussion of Related Art
Processors such as those used in commercially available computers (PC) include ever increasing connections. In the future, up to 1024 connections are expected, serving for transmitting data and/or power from and to a processor core. The frequencies at which the data is transmitted lie in the gigahertz range.
Every IC is checked and tested with regard to its function between the various production steps and during the final inspection. The prior art discloses for this purpose so-called test devices which nowadays comprise a so-called test or load board. In the case of these load boards, many serial connections are led from a test head to a measuring station. Data rates of up to 6 Gbps are typically achieved at the present time. In the future, data rates of up to 15 Gbps or more are to be expected. A hundred channels per square inch are advantageous on account of the confined space conditions on the load board and the preferably shortest possible PCB connections. Current devices no longer satisfy present-day demands or have a complicated, costly construction.
A chip has contact arrays having a diameter of a few μm, which are to be connected to the measuring apparatus (tester). The prior art uses planar structures for signal lines on PCBs (printed circuit boards), so called microstrips. A microstrip adversely impairs the signal since the attenuation increases as the line length increases. In order to make contact with several hundred pins, very long lines have to be used nowadays. Moreover, high precision is required. A further problem consists in the high mechanical loads which can occur since contact has to be made with each pin with a comparatively high force in order that a secure connection results.
The prior art discloses devices for testing chips having a multiplicity of connections. For each chip, an exchangeable load board is specifically coordinated with the respective chip. Alongside the connections, said load board can also have electronics. The solutions known from the prior art have a two-dimensional, planar construction in which connections which are grouped around a contact array and lie in a plane or parallel with respect thereto serve for connecting the load board to the test machine. These load boards are very large in their construction and additionally have mechanical disadvantages. Moreover, they have a comparatively complicated construction.
U.S. Pat. No. 4,931,726 in the name of Hitachi, Ltd. was published in 1988 and describes a test device for testing chips arranged or respectively soldered on circuit boards. The test device is pressed from above onto the circuit board with the chip. Coaxial connectors are shown schematically and are intended to serve at one end for making contact with conductor tracks or soldered joints on the circuit board. At the other end, the cables are held in two plate-like connection regions butting directly against one another at an angle and contact is made with said cables there by means of spring pins. Continuous coaxial signal routing does not take place, which results in an impairment of the signal quality. The principle shown is not suitable for high channel densities.
US2007/167083 in the name of Advantest was published in 2007 and describes a connector housing block having a very large construction and serving for electrically connecting a test head to connectors of a test device. A chip is arranged on a first plane for test purposes and is operatively connected by means of electrical lines to connectors arranged on a second, parallel plane. Certain parts are mounted in floating fashion.
U.S. Pat. No. 5,896,037 from Method Electronics, Inc. was published in 1999 and discloses a type of test adapter for testing chips. The test adapter has a multilayered construction. The individual connectors are connected via conductor tracks. The test adapter has a two-dimensional construction, that is to say that all the connections are situated in one plane.